The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board (PCB) attached to a disk drive base of the HDA. The head disk assembly includes at least one disk (such as a magnetic disk, magneto-optical disk, or optical disk), a spindle motor for rotating the disk, and a head stack assembly (HSA). The spindle motor typically includes a rotating hub on which disks mounted and clamped, a magnet attached to the hub, and a stator. Various coils of the stator are selectively energized to form an electromagnetic field that pulls/pushes on the magnet, thereby rotating the hub. Rotation of the spindle motor hub results in rotation of the mounted disks. The printed circuit board assembly includes electronics and firmware for controlling the rotation of the spindle motor and for controlling the position of the HSA, and for providing a data transfer channel between the disk drive and its host.
The head stack assembly typically includes an actuator, at least one head gimbal assembly (HGA), and a flex cable assembly. Each HGA includes a head for reading and writing data from and to the disk. In magnetic recording applications, the head typically includes an air bearing slider and a magnetic transducer that comprises a writer and a read element. The magnetic transducer's writer may be of a longitudinal or perpendicular design, and the read element of the magnetic transducer may be inductive or magnetoresistive. In optical and magneto-optical recording applications, the head may include a mirror and an objective lens for focusing laser light on to an adjacent disk surface.
During operation of the disk drive, the actuator must rotate to position the heads adjacent desired information tracks on the disk. The actuator includes a pivot bearing cartridge to facilitate such rotational positioning. One or more actuator arms extend from the actuator body. An actuator coil is supported by the actuator body opposite the actuator arms. The actuator coil is configured to interact with one or more fixed magnets in the HDA, typically a pair, to form a voice coil motor. The printed circuit board assembly provides and controls an electrical current that passes through the actuator coil and results in a torque being applied to the actuator. A crash stop is typically provided to limit rotation of the actuator in a given direction, and a latch is typically provided to prevent rotation of the actuator when the disk dive is not in use.
Many modern HDAs include a ramp adjacent the disk outer diameter. In such HDAs, each HGA (itself attached to the distal end of an actuator arm in the HSA) typically includes a lift tab. The lift tab is designed to contact a lift tab supporting surface of the ramp when the actuator moves near an extreme position that is typically beyond the disk outer diameter. The interaction between the lift tab and the lift tab supporting surface serves to unload the heads from the surface of the disk when the disk drive is not in use. The benefits of unloading the heads can include improved tribological performance and reliability of the head-disk interface and improved robustness to mechanical shocks that are suffered under non-operating conditions.
However, to prevent the heads from sliding off of the outer edge of the disk before they are properly unloaded, a portion of the ramp (that includes a portion of the lift tab supporting surface) typically must extend over the disk outer diameter. That portion of the ramp overlaps the disk. A consequence of such overlap is that the ramp typically must be removed before the disk(s) or spindle can be removed for rework.
Rework is a significant and costly part of disk drive manufacture; as much as 25% of initially manufactured disk drives require rework. Of course the actuator arms and heads must be completely demerged and unloaded before the disk(s) or spindle can be removed for rework. But the ramp can not facilitate such demerge and unloading after the ramp is removed. Consequently, with contemporary ramp designs, the HSA must be removed using a transfer comb prior to rework or replacement of the disk(s) or spindle.
There are many problems associated with removing the HSA as a prerequisite to rework of the disk(s) or spindle. Firstly, there is the additional time and associated cost of the additional HSA-removal process steps. Secondly, some causes of disk or spindle rework do not imply that there is anything initially wrong with the HSA (e.g. if the servo pattern needs to be externally rewritten, or if the spindle must be replaced, etc). However, after removal, handling, storage, cleaning, and replacement of the relatively expensive and delicate HSA, the HSA itself may then become damaged—by rework intended to remedy an unrelated problem with the disk(s) or spindle. For example, removal of the HSA typically requires prior insertion of a transfer comb that contacts the fragile HGAs. The transfer comb is typically an inexpensive plastic part that has poor dimensional tolerances relative to the ramp, and that can damage the HGAs during insertion. Also for example, cleaning of the HSA typically requires prior removal of its pivot bearing, typically wasting the pivot bearing attachment means (e.g. tolerance ring or C-clip).
Thus, there is a need in the art for an improved ramp configuration that can allow disk or spindle rework/replacement without the need to remove the HSA from the HDA.